SENSES OF BATS — VESEY-FITZGERALD 323 



er's, and, after the bats had left the hole for the evening flight, netted 

 the entrance. I caught many bats (and at almost all hours of the 

 night) in the nets, trying to get back to the holes. At that time nothing 

 was known about supersonic vibrations in connection with bats, and I 

 did not think that there was anything odd about it. But in the sum- 

 mer of 1946, realizing that the supersonic tone should have warned 

 them of an obstruction, I repeated the process at dens of noctule, 

 whiskered, Daubenton's, and serotine, with the same result. The bats 

 appeared to be quite unaware that there was an obstruction and flew 

 straight into the nets. Later I covered the entrance hole to a noctule 

 den with thick brown paper, and even this did not seem to be indicated 

 to the bats, which flew straight into it. Before returning to their 

 den noctules fly around the tree and in and out among the branches 

 with never a false movement, yet they are unaware of an obstruction at 

 the veiy entrance to their sleeping quarters. It seems evident that 

 echo-location, for some reason, is shut off at that moment. 



On the other hand, it seems to operate to some extent during hiber- 

 nation. Everyone who has entered a hibernaculum of bats must have 

 noticed the tremor that goes through the sleeping creatures at the first 

 presence of a stranger. They are asleep, and incapable of movement, 

 but there can be no doubt at all that they are aware. 



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1943. Journ. Soc. Pres. Fauna Emp., vol. 38, p. 10, 



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1945. Discovery, September. 



